Conventionally, some sound rooms and audio rooms, which are used for instrument playing, movie appreciation, and other sound-related events, are equipped with a soundproof structure that prevents sound generated inside the room from leaking outside the room, as well as a sound absorbing structure that eliminates standing waves remaining in corners of the room in order to improve acoustics that instrument players and listeners perceive in the room and that absorbs sounds in some audio frequency ranges generated in the room and reflected off on walls of the room in order to enhance the reverberation of the sound in the room. Conventionally used sound absorbing structures in rooms include sound absorbing panels and sound absorbing materials.
Technologies relating to absorption of sound generated in a room are disclosed in Japanese Unexamined Utility Model Application Publication No. 1987(SHO62)-42607 (Patent Literature 1) and Japanese Unexamined Patent Application Publication No. 2007-286387 (Patent Literature 2). According to the sound room disclosed in Patent Literature 1, bass absorbers having a approximately triangular cross section are installed along almost the entire length of joints between walls and the ceiling of a room, two surfaces of each bass absorber fitting along a wall and the ceiling, respectively, and one surface facing obliquely downward to the inside of the room. Patent Literature 1 intends to effectively absorb low-pitched sounds with these bass absorbers. Patent Literature 2 discloses a sound improving member for improving sound in a structure. The sound improving member is installed at the boundary between structure surfaces that compose the structure in two directions or three directions, and includes a positioning section in contact with the structure surfaces and a tilted face that is inclined relative to the structure surfaces in two directions or three directions while the positioning section is in contact with the structure surfaces to effect positioning. The tilted face of the sound improving member reflects or absorbs sound to improve the sound inside the structure.